Reducing the curing rate of buta-diene-styrene copolymer rubber



, Patented a. 14, "1941 REDUCING THE CURING RATE OF BUTA- DIENE-STIRENE COPOLYMER RUBBER Robert R. Sterrett, Naugatuck, Conn., assignor to United States Rubber Company, New N. Y., a corporation of New Jersey York,

No Drawing. Application January 15, 1944, Serial No. 518,416

. 1 i 1 This invention relates to improvements in curing rubbery copolymers of butadiene and styrene. It is known that chlorinated quinones such as tetrachlorpara-benzoquinone, in the presence of certain oxidizing agents, vulcanize said copolymer rubbers. The vulcanization is quite rapid, and in many instances results in scorched stocks which causes waste and delay. Scorch is defined as a premature partial vulcanization of the stock brought about by heat present or developed during processing. A scorched stock is no longer completely thermoplastic and cannot be smoothly sheeted or extruded.

I have found that by adding a thiuramdisulfid having the structure =N-('%SSCN= in which the terminal nitrogen is bonded to aliphatic hydrocarbon radicals such as alkyl or cy-' cloalkyl (e. g., ethyl, butyl, amyl, cyclopentamethylene), benzyl, etc., and particularly a tetraderstood that the invention is not to be limited thereto:

EXAMPLE 5 Master batch GR-S (butadiene-1,3-styrene copolymer rubber) 100.0 Treated whiting 100.0 Special whiting 30.0 Mineral rubber 12.0 Zinc oxide 15.0 Stearic acid 0.75

- Above M. 13..-; 251.15 251.15 251.15

Tetrachloro Para-benzoquinoue 0. 6 0. 6 0.6 TetramethylThiuramdisuliide. 1.0 20 no, 8.0 8.0 8.0

I Q Scorch test at 239 F.

A B c TimemMhmm tlsq in g? #lsq in E5" 5/50 in gf gi on.a on,a as. Tensile i Tensile Break Tens1le Break 560 a 32s 456 267 410 000 m 023 010 288 590 120 550 420 e23 330 510 053 406 656 314 003 rate of cure can be greatly reduced and scorching prevented. Based on 100 parts, by weight, of the butadiene-IB-styrene- 'copolymer rubber the amount of the disulfide is proportioned, according to the amount of the said vulcanizing agent used,

to be in amount suificient to properly set the .stock with substantially no scorching. Generally,

the amounts used may range from .01 to about 4 I parts of the disulfide per 100 parts of the rubber, although in certain cases more may be used.

There is a progressive reduction in rate of cure as the tetramethyl thiuramdisulfide is increased.

While I have shown various embodiments of the invention, it is to be understood that the invention is susceptible of those modifications which appear within the spirit of the invention and the scope of the appended claim, for example, other substituted thiuramdisulfides than the tetrasubstituted materials may be used, e. g., the disubstituted thiuramdisulfides such as dibenzyl thiuramdisulfide.

Having thus described my invention, what I claim and desire to protect by Letters Patent is;

: A method of reducing the rate of cure of a The f l win example. in Which t e parts are rubber-like copolymer of butadiene-1,3 and sty- 2,429,080 I 3- 4 rene with an oxidizing agent and tetrachlor p-. i benzoquinone, which comprises additionally add- REFERENCES CITED ing to the stock before cure from .01 to 4 parts The following references are or z ecord in the by weight of a. thiuramdisulfide in whicheach flle of this patent: nitrogen atom is bonded to aliphatic hydrocarbon 5 radicals, per 100 parts by weight of the copolymer UNITED STATES PATENTQ Number Name Date rubber.

1,918,328 Fisher July 18, 1933 ROBERT R. STERBETT. 2,234,204 Starkweather Mar. 11,1941 

